1. Field of the Invention
The invention relates to run-free, wholly elastic fabrics and methods of making the same. In particular, the invention is directed to elastic textile fabrics that are produced by knitting only elastic yarns together to obtain a run-free, wholly elastic fabric. Advantageously, the method of the invention makes it possible to obtain run-free, wholly elastic fabrics without the need to knit the elastic yarn with natural or other synthetic fibers. The invention also relates to wholly elastic warp knitted fabrics comprising an inlaid yarn. The inlay may be an elastomeric or non-elastomeric warp yarn, weft insertion yarn or combination thereof.
2. Description of the Prior Art
At the time the invention was made, it was not known how to produce a wholly elastic textile fabric of any construction that would not run. The state of the art was such that Lycra(copyright) spandex (DuPont) was never used alone, but combined with natural and manmade fibers in all fabric constructions. Therefore, in order to manufacture a warp knitted elastic fabric with acceptable non-run characteristics, it was necessary prior to the invention to knit the elastic yarn with a natural or other synthetic yarn. Alternatively, various elastic warp knitted fabrics are known wherein non-elastic yarn is formed into a fabric or a mesh to bind and hold inlaid elastic threads within the structure.
Prior art patents disclosing warp knitted elastic fabrics include U.S. Pat. Nos. 3,931,721 (Adamson), 4, 107,956 (Parsons), 4,688,403 (Gajjar) and 5,832,749 (Anonietti). U.S. Pat. No. 3,931,721 describes a warp knitted elastic fabric composed of alternating non-elastic courses formed from non-elastic yarns and interweaving elastic courses formed primarily with elastic thread. There is no disclosure or suggestion that the method of U.S. Pat. No. 3,931,721 could be used to knit elastic yarns to prepare run-free, wholly elastic warp knitted fabrics. Intervening non-elastic courses are an integral part of the knitted fabric structure of the U.S. Pat. No. 3,931,721.
U.S. Pat. No. 4,107,956 is directed to a method for warp knitting a narrow clasp fastener carrier tape not exceeding four inches in fill and finished width. A three guide bar construction is employed in which the front guide bar knits a pillar stitch and the middle guide bar performs a two needle overlap in successive courses. The back guide bar lays-in over three or more needles. It is disclosed that the method of U.S. Pat. No. 4,107,956 may be practiced with nylon yarns and blends thereof derived from other synthetic polymers, e.g., polyacrylics, polyesters and materials such as glass. However, there is no disclosure or suggestion that it would be feasible to use elastomeric yarns to warp knit an elastic fabric that is run-free.
U.S. Pat. No. 4,688,403 discloses a method of knitting fabrics with elastomeric and non-elastomeric threads that have surface interest. A single needle bar is fed from a front or first bar of non-elastomeric knitting yarns, e.g., nylon yarn, and a plurality of back bars of elastomeric knitting yarns, e.g., spandex yarn. U.S. Pat. No. 5,832,749 describes a method of making an elastic knitwear fabric by weaving a first thread with elastic or elastomeric characteristics, e.g., Lycra(copyright) thread, with a second thread with non-elastic characteristics, e.g., nylon 6. The non-run quality of the fabric is said to be due to the fact that the elastic thread and the non-elastic thread work in opposition during knitting. However, each of U.S. Pat. Nos. 4,688,409 and 5,832,749 lack any meaningful suggestion of knitting elastomeric yarns to produce run-free, wholly elastic warp knit fabrics.
Notwithstanding the many prior art examples of elastic warp knitted fabrics comprised of a plurality of elastic and non-elastic threads, there remains a need to produce a wholly elastic warp knitted fabric with high non-run characteristics.
For purposes of describing the present invention, the expression xe2x80x9celastic yarnxe2x80x9d shall be understood to mean the types of elastic fibers or yarns that are generically known as spandex in the United States and Canada and as elastane in Europe. The term xe2x80x9cspandexxe2x80x9d has its usual definition, i.e., a long chain synthetic polymer that comprises at least 85% by weight segmented polyurethane. An example of a commercial brand of an elastic yarn that can be used in the invention is sold by DuPont under its Lycra(copyright) trademark. Thus, the expression xe2x80x9celastic yarnxe2x80x9d as used herein shall include elastic or elastomeric fibers and yarns having the composition and properties that are typical of spandex- and elastane-type fibers. By definition, such xe2x80x9celastic yarnxe2x80x9d shall exclude more than traces of other than elastic or elastomeric fibers or filaments. It follows, therefore, that the expression xe2x80x9cwholly elasticxe2x80x9d when used to describe embodiments of the invention shall mean xe2x80x9celastic yarnxe2x80x9d alone.
According to one embodiment of the present invention, a wholly elastic warp knitted fabric is produced on a warp knitting machine comprising knitting elements including a needle bar and at least two guide bars for stitching in varying proximity to the needle bar. To be discussed in connection with other embodiments of the invention, the warp knitting machine may be further comprised of one or more inlay bars and weft insertion devices. However, the method of this first embodiment comprises threading the guide bars for stitching with an elastic yarn, and knitting the elastic yarn together by moving the knitting elements to produce a series of stitches forming the knitted fabric. During knitting, the guide bar for stitching that is closest to the needle bar knits a substantial number of pillar stitches. Depending upon the movement of this guide bar, open or closed stitches can be produced. The pillar stitch is preferably a closed pillar stitch. In accordance with this same embodiment, at least one of the other guide bars for stitching performs a substantial number of two needle overlap constructions or knits a substantial number of pillar stitches.
According to another embodiment of the present invention, the wholly elastic warp knitted fabric of the invention is produced by moving the guide bar for stitching closest to the needle bar to perform a substantial number of two needle overlap constructions. In this embodiment, at least one of the other guide bars for stitching knits a substantial number of pillar stitches, preferably closed pillar stitches.
The invention is also directed to wholly elastic warp knitted fabrics comprising an inlaid yarn which is held or trapped into the structure of the knitted fabric. In accordance with the invention, the inlaid yarn may be an elastomeric or non-elastomeric warp yarn, weft insertion yarn or combinations thereof. Laying-in is achieved by means of inlay bars and weft insertion devices during knitting of the elastic fabric. Examples of the inlaid nonelastomeric material include, but are not limited to natural fibers and other synthetic fibers such as aramid, nylon, polyester, polypropylene, acrylic, glass, carbon and metallic fibers or yarns. Natural fibers which are suitable for use in the invention include, but are not limited to cotton, linen, sisal, hemp, wool, silk, kenaf and coconut fiber.
The methods of the invention can be used to produce a textile fabric of any pattern or structure, e.g., a warp knitted fabric with a regular surface or a net structure. Therefore, depending upon the structure and pattern of the fabric to be produced, the guide bars and inlay bars may be threaded in a variety of ways to produce a specific construction and pattern. As such, the guide bars and inlay bars, independent of each other, may be fully threaded or partly threaded. The fabrics produced in accordance with the invention may be used as complete fabrics. Alternatively, the fabrics of the invention may be sown or combined with other fabrics and materials for a particular application.
The wholly elastic warp knitted fabrics of the present invention are uniquely and advantageously run-free. The properties of these fabrics are advantageously enhanced by laying in a warp or weft insertion yarn in the structure of the fabric during knitting of the elastic warp knitted fabric.